In an integrated circuit device, a semiconductor chip formed with an integrated circuit is accommodated in a package. To reduce power consumption in an integrated circuit device packaged in a battery-driven electronic machine such as a portable telephone or a portable information terminal, a power supply generating circuit that generates an internal power supply voltage by reducing an external power supply voltage is built into the device. A DCDC converter or the like, for example, is available as this power supply generating circuit.
Meanwhile, to protect an integrated circuit device from static electricity, an electrostatic protection circuit is provided at an input/output terminal coupled to an external terminal of the package. Under normal usage conditions, the electrostatic protection circuit does not operate, but when a voltage between the input/output terminal and a ground terminal increases rapidly due to application of a static electricity charge or the like, the electrostatic protection circuit operates to absorb the applied charge.
This type of electrostatic protection circuit is described in Japanese Laid-open Patent Applications No. 2007-142423, No. 2007-59444, and No. 2007-202194, for example.
During a normal operation, a power supply generating circuit such as a DCDC converter generates a power supply voltage by supplying a current from an external power supply by means of pulse driving in accordance with a consumed current of a load circuit to which the generated power supply voltage is to be supplied. Noise may be generated in a wire of the external power supply due to the pulse driving, and this noise may cause the electrostatic protection circuit to malfunction.
Further, in an integrated circuit to which a power supply voltage generated by a power supply generating circuit is supplied, the generated power supply voltage may rise rapidly when the power supply generating circuit is activated, causing an electrostatic protection circuit provided at a power supply voltage supply terminal to operate in order to suppress the rise of the power supply voltage, and as a result, the rise of the power supply voltage may be impeded.